1. Field of the Invention
The present invention relates to a liquid crystal display apparatus, and more particularly, to a liquid crystal panel incorporating a "chips-on-glass" (COG) system wherein integrated circuit (IC) chips are directly mounted on a glass substrate. Also, the present invention is directed to a method of manufacturing a COG type liquid crystal panel.
2. Description of the Related Art
Since a liquid crystal display apparatus display has advantages including a light weight, a small thickness, a low power consumption and so on, its applications have been steadily enlarged. The liquid crystal display apparatus includes a picture display having picture elements or pixels of liquid crystal arranged in a matrix pattern, and driving IC chips, hereinafter referred to as D-IC chips, for driving the liquid crystal display. Recently, a liquid crystal display apparatus has been manufactured using the COG system in which D-IC chips are directly mounted on the edge of a glass substrate. Also, the COG type liquid crystal panel makes use of a flexible printed circuit (FPC) film for applying signals to the D-IC chips.
In such a COG type liquid crystal panel, since the D-IC chips and the FPC film are mounted at different positions on the glass substrate, the effective field area is small and the size of liquid crystal panel is large. Further, the FPC film includes a wiring for commonly applying electric signals to all the D-IC chips. This results in an increase in the wiring amount of the FPC film, as well as an increase in the manufacturing cost of FPC film and an increase in the manufacturing cost of liquid crystal panel.
For example, as shown in FIG. 1A and FIG. 1B, the COG type liquid crystal panel includes D-IC chips 6 mounted on the edge of a lower glass substrate 4 in such a manner to be positioned between an upper glass substrate 2 and a FPC film 8. A picture display having liquid crystal cells and thin film transistors (TFTs) arranged in a matrix pattern is formed between the lower glass substrate 4 and the upper glass substrate 2. The edge of the lower glass substrate 4 mounted with the D-IC chips 6 and the FPC film 8 is usually referred to as a "pad area" because electrode pads for supplying signals to drive the TFTs are located at the edge of the lower glass substrate 4. In this pad area, output wiring electrodes (not shown) are provided for connecting the D-IC chips 6 with the picture display and input wiring electrodes (not shown) are provided for connecting the D-IC chips 6 and the FPC film. The D-IC chips 6 are provided to drive the TFTs and are adhered to the pad area via an anisotropic conductive film (ACF) 10 and bumps 10A in such a manner to be electrically connected to the input and output wiring electrodes. The FPC film 8 is mounted with a wiring for transferring electrical signals, e.g., video data signals, timing control signals and voltage signals, from a control circuit (not shown) to the D-IC chips 6. Such a FPC film 8 also is adhered to the pad area via the ACF 10 and the bumps l0A in such a manner to be electrically connected to the input wiring electrodes.
As described above, in the conventional COG type liquid crystal panel, the D-IC chips and the FPC film are mounted in parallel at the pad area, causing the pad area to be enlarged. As a result of this mounting arrangement, the field area becomes small and the size of glass substrate becomes large. Further, in the conventional COG type liquid crystal panel, the FPC film is adhered to the pad area on the lower glass substrate such that it is located at positions corresponding to locations of all of the D-IC chips. This results in an increase in a wiring amount located at the FPC film and an increase in the manufacturing cost of the FPC film and a increase in the manufacturing cost of the liquid crystal panel.